JP7651338B2 - Blast furnace operation method - Google Patents

Description

The present invention relates to a method for operating a blast furnace.

In the steel industry, the blast furnace process is the mainstream of pig iron manufacturing processes. In the blast furnace process, ferrous raw materials (raw materials containing iron oxide, mainly sintered ore, hereinafter also referred to simply as "ferrous raw materials") and coke are charged alternately and in layers into the blast furnace from the top of the furnace, while hot air is blown into the blast furnace from the tuyere at the bottom of the furnace. The hot air reacts with the pulverized coal blown in together with the hot air and the coke in the blast furnace to generate high-temperature reducing gas (mainly CO gas in this case). In other words, the hot air gasifies the coke and pulverized coal. The reducing gas rises in the blast furnace and reduces the ferrous raw materials while heating them. The ferrous raw materials descend in the blast furnace, while being heated and reduced by the reducing gas. The ferrous raw materials then melt and drip into the blast furnace while being further reduced by the coke. The iron-based raw materials are eventually stored in the hearth as molten pig iron (pig iron) containing just under 5% by mass of carbon. The molten pig iron in the hearth is removed from the tap hole and used in the next steelmaking process. Therefore, in the blast furnace process, carbonaceous materials such as coke and pulverized coal are used as reducing agents.

Recently, the prevention of global warming has been called for, and the reduction of carbon dioxide ( _CO2 gas) emissions, which is one of the greenhouse gases, has become a social issue. As described above, the blast furnace process uses carbonaceous materials as a reducing agent, which generates a large amount of _CO2 gas. Therefore, the steel industry is one of the major industries in terms of _CO2 gas emissions, and must respond to this social demand. Specifically, there is an urgent need to further reduce the reducing agent ratio (amount of reducing agent used per ton of molten iron) in blast furnace operation.

The reducing agent has the role of raising the temperature of the charge by becoming heat in the furnace and the role of reducing the iron-based raw materials in the furnace, and in order to reduce the reducing agent ratio, it is necessary to increase the reduction efficiency in the furnace. The reduction reaction in the furnace can be expressed by various reaction formulas. Among these reduction reactions, the direct reduction reaction by coke (reaction formula: FeO + C ⇒ Fe + CO) is an endothermic reaction accompanied by a large heat absorption. Therefore, it is important to prevent this reaction from occurring as much as possible in reducing the reducing agent ratio. Since this direct reduction reaction occurs in the lower part of the blast furnace, if the iron-based raw materials can be sufficiently reduced by reducing gas such as CO and _H2 before they reach the lower part of the furnace, the iron-based raw materials that are the subject of the direct reduction reaction can be reduced.

As a conventional technique for solving the above problems, for example, as disclosed in Patent Documents 1 to 6, a technique is known in which reducing gas potential in a furnace is improved by blowing reducing gas ( _H2 gas, COG, natural gas, city gas, etc.) together with hot air from a tuyere or shaft. When the reducing gas is a carbon-containing reducing gas (a reducing gas whose molecular structure contains carbon atoms, for example, a hydrocarbon gas), the carbon atoms in the carbon-containing gas become CO gas in the blast furnace and reduce the iron-based raw materials. When the reducing gas is hydrogen gas ( _H2 gas), the hydrogen gas reduces the iron-based raw materials. This makes it possible to reduce the amount of iron-based raw materials that are the subject of a direct reduction reaction.

Patent No. 6019893 Patent No. 5987773 Patent No. 5050706 Patent No. 5770124 Patent No. 5315732 Patent No. 5851828 Patent No. 6119700

However, these techniques do not take into consideration the properties of the coke when the reducing gas is injected, and the effect of reducing _CO2 emissions is small. Although Patent Document 7 refers to the properties of the coke, the technique disclosed in Patent Document 7 cannot be said to be sufficient in reducing _CO2 emissions.

Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide a new and improved blast furnace operation method capable of further reducing _CO2 emissions.

In order to solve the above problems, according to one aspect of the present invention, there is provided a method for operating a blast furnace, comprising: a first step of creating correlation information showing a correlation between coke reactivity and _CO2 gas reduction information showing a _CO2 gas reduction effect for each amount of hydrogen-containing gas containing hydrogen gas injected into the blast furnace or for each hydrogen concentration in the bosh gas; a second step of determining an appropriate value of coke reactivity based on the correlation information and the amount of hydrogen-containing gas injected into the blast furnace or the hydrogen concentration in the bosh gas; and a third step of charging the blast furnace with coke having the determined appropriate value.

Here, the correlation information indicates the correlation between the reactivity of the coke and the carbon consumption unit, and in the second step, the coke reactivity that minimizes the carbon consumption unit relative to the amount of hydrogen-containing gas injected into the blast furnace or the hydrogen concentration in the bosh gas may be determined as the appropriate value of the coke reactivity.

In addition, in the second step, optimum value information is prepared that indicates the correlation between the total amount of hydrogen input to the blast furnace or the hydrogen concentration in the bosh gas and the optimum value of the coke reactivity, and the optimum value of the coke reactivity is determined based on the optimum value information and the total amount of hydrogen input to the blast furnace or the hydrogen concentration in the bosh gas.

In addition, in the first step, an approximation curve showing the correlation between the coke reactivity and the _CO2 gas reduction information may be created as correlation information, and in the second step, the coke reactivity corresponding to the inflection point of the approximation curve may be determined as an appropriate value of the coke reactivity.

According to the above aspect of the present invention, it is possible to further reduce _CO2 emissions.

1 is a graph showing the correlation between coke reactivity (CRI) (%) and carbon consumption intensity (Input C) (kg/t) for each amount (Nm ³ /t) of hydrogen gas injected at room temperature (25° C.). 2 is a graph showing an approximation curve of the correlation in FIG. 1 . 1 is a graph showing the correlation between total hydrogen input (Nm ³ /t) to a blast furnace and coke reactivity (CRI) (%). 1 is a graph showing the correlation between hydrogen concentration (%) in bosh gas and coke reactivity (CRI) (%). 1 is a graph showing the correlation between coke reactivity (CRI) (%) and carbon consumption intensity (Input C) (kg/t) for each injection amount (Nm ³ /t) of high-temperature (1200° C.) hydrogen gas or high-concentration hydrogen-containing gas.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. In this embodiment, a numerical range expressed using "to" means a range including the numerical values written before and after "to" as lower and upper limits. Furthermore, "carbon consumption intensity (Input C)" is the amount of carbon required to produce 1 ton of molten iron (i.e., carbon consumption per ton of molten iron) (kg/t). "Reduction rate of carbon consumption intensity (Input ΔC)" means the reduction rate of carbon consumption intensity relative to base operation (operation without injecting hydrogen-containing gas). If Input C of base operation is A (kg/t) and Input C during a certain operation is B (kg/t), Input ΔC is expressed by the following formula.
Input △C=(AB)/A×100(%)
The greater the reduction rate of the carbon consumption intensity, the greater the reduction in the reducing agent ratio (the amount of coke and pulverized coal consumed per ton of molten iron), and thus the greater the reduction in _CO2 emissions.

1. Findings by the Inventor
In order to solve the above problem, the present inventors focused on the amount of hydrogen gas injected into the blast furnace and the reactivity of the coke, more specifically, the CRI (Coke Reactivity Index). Here, the reactivity of the coke refers to the ease of the gasification reaction of the coke by _CO2 gas and _H2O gas. The gasification reaction of the coke by _CO2 gas is represented by C+ _CO2⇒2CO , and the gasification reaction of the coke by _H2O gas is represented by C+ _H2O⇒CO + _H2 . The CRI is an index obtained by the following process. That is, 200 g of coke adjusted to a size (particle size) of 20±1 mm is reacted under the conditions of gas composition: _CO2 (100 mol%), reaction temperature 1100°C, and reaction time 2 hours. Next, the mass of the sample after the reaction is measured, and (mass before reaction-mass after reaction)/mass before reaction×100 is calculated. This is referred to as the CRI. Therefore, the CRI is an index that indicates the mass reduction rate due to the gasification reaction of the coke.

The present inventors have found that when the amount of hydrogen gas injected is increased, the reactivity of the coke is decreased, thereby making it possible to further improve the effect of reducing _CO2 emissions.

In blast furnace operation without injecting reducing gas such as hydrogen gas, i.e., in normal blast furnace operation, it is generally known that the use of high reactivity coke can reduce _CO2 emissions. This is because the reduction of iron-based raw materials is promoted by CO gas and hydrogen gas generated by the gasification reaction of coke (C + _CO2 ⇒ 2CO, C + _H2O ⇒ CO + _H2 ), and the ratio of direct reduction, which is a large endothermic reaction, decreases. The present inventor has found that, in contrast to the conventional technology, the use of low reactivity coke can reduce _CO2 emissions when performing operation in which a large amount of hydrogen gas is injected. The present inventor considers the mechanism as follows.

The reduction rate by hydrogen gas (the rate at which iron-based raw materials are reduced) is faster than that by CO gas, so when a large amount of hydrogen gas is injected into the furnace, the hydrogen reduction ratio (the ratio of the reduction reaction by hydrogen gas among the reduction reactions of iron-based raw materials) increases. The reduction reaction of iron-based raw materials by hydrogen gas (hydrogen reduction) is an endothermic reaction, which causes the temperature inside the furnace to decrease. When the amount of hydrogen gas injected is small, the endothermic reaction by hydrogen reduction does not become the rate-limiting factor for the heat balance inside the furnace. However, if a large amount of hydrogen gas is injected and the hydrogen reduction ratio increases excessively, the temperature inside the furnace drops significantly and the reduction rate of iron-based raw materials by hydrogen gas and CO gas begins to decrease.

Here, the gasification reaction of coke by _H2O gas (C+ _H2O⇒CO + _H2 ) is an endothermic reaction, and when highly reactive coke is used in an operation in which a large amount of hydrogen gas is injected, not only the endothermic reaction due to hydrogen reduction but also the endothermic reaction due to the gasification reaction of coke by _H2O gas occurs frequently in the furnace. Therefore, there is a concern that the temperature in the furnace will drop significantly, and the speed of each reduction reaction occurring in the furnace will drop significantly.

The inventors therefore considered that in operations in which a large amount of hydrogen gas is injected, it would be effective to reduce the amount of endothermic reaction by lowering the reactivity of the coke, thereby preventing a drop in the furnace temperature. If the reactivity of the coke decreases, the amount of regenerated reducing gas in the furnace decreases, raising concerns that the reduction reaction rate will decrease. However, in operations in which a large amount of hydrogen gas is injected, it is believed that the benefits of preventing a drop in the furnace temperature outweigh the disadvantages of a decrease in the reactivity of the coke.

In other words, the inventors considered that the more the amount of hydrogen gas injected into the blast furnace is increased, the more effective it is in reducing the reactivity of the coke in reducing _CO2 emissions. Based on this knowledge, the inventors have come up with a method for operating a blast furnace according to this embodiment. Hereinafter, this embodiment will be described in detail.

<2. Blast furnace operation method>
(2-1. First step)
The blast furnace operation method according to the present embodiment includes the following first to third steps. In the first step, correlation information is created that indicates a correlation between the reactivity of coke and _CO2 gas reduction information that indicates a _CO2 gas reduction effect for each amount of hydrogen-containing gas containing hydrogen gas injected into the blast furnace or for each hydrogen concentration in the bosh gas. Here, the amount of hydrogen-containing gas injected into the blast furnace is the amount of hydrogen-containing gas injected into the blast furnace per ton of molten iron, and the hydrogen concentration in the bosh gas is the hydrogen gas concentration (mol%) in the bosh gas.

As described above, the more the amount of hydrogen gas injected into the blast furnace increases, the more effective it is in reducing _CO2 emissions to reduce the reactivity of the coke. Therefore, there is a correlation between the reactivity of the coke and the _CO2 gas reduction information showing the effect of reducing _CO2 gas, and such a correlation differs depending on the amount of hydrogen-containing gas injected into the blast furnace or the hydrogen concentration in the bosh gas. Therefore, in the first step, correlation information showing such a correlation is created.

Here, the hydrogen-containing gas may contain hydrogen gas, but is preferably a high-concentration hydrogen-containing gas containing 80 mol% or more of hydrogen gas, and more preferably hydrogen gas (pure hydrogen gas). Gases contained in the hydrogen-containing gas include hydrogen gas, various reducing gases (COG, natural gas, city gas, etc.), nitrogen gas, etc. The hydrogen-containing gas is blown into the blast furnace from the tuyere.

The reactivity of the coke is, for example, the CRI described above. _{The CO2} gas reduction information may be any information indicating the effect of reducing _CO2 gas, for example, the carbon consumption intensity (Input C). The _CO2 gas reduction information may be the reduction rate of the carbon consumption intensity (Input ΔC), etc. As described above, the carbon consumption intensity is the carbon required to produce 1 ton of molten iron (i.e., the carbon consumption per ton of molten iron). Here, carbon basically refers to carbon (carbon atoms) in the coke and pulverized coal, but when the hydrogen-containing gas contains a gas containing carbon, the carbon in such a gas is also included.

Correlation information showing the correlation between the reactivity of coke and the _CO2 gas reduction information can be obtained, for example, by a blast furnace operation simulation. Details will be described in the examples, but in this embodiment, a so-called "blast furnace mathematical model" shown in Kouji TAKATANI, Takanobu INADA, Yutaka UJISAWA, "Three-dimensional Dynamic Simulator for Blast Furnace", ISIJ International, Vol. 39 (1999), No. 1, p. 15-22, etc. is used. This blast furnace mathematical model roughly defines a plurality of meshes (small regions) by dividing the internal region of the blast furnace in the height direction, the radial direction, and the circumferential direction, and simulates the behavior of each mesh. Operational conditions including the reactivity of coke and the amount of hydrogen-containing gas injected are input into this blast furnace mathematical model to obtain _CO2 gas reduction information. It is preferable that the operational conditions input into the blast furnace mathematical model are the same as the actual blast furnace operation conditions. An example of the results is shown in Figure 1.

The horizontal axis of Fig. 1 indicates CRI (%), and the vertical axis indicates carbon consumption intensity (Input C) (kg/t). Therefore, in the example of Fig. 1, the coke reactivity is CRI, and the _CO2 gas reduction information is carbon consumption intensity. Point P10 indicates the correlation between CRI and carbon consumption intensity when the amount of hydrogen gas injected is 0 ^Nm3 /t (amount injected per ton of molten iron) (so-called normal operation), and graph L10 is a linear connection of points P10.

Point P11 shows the correlation between CRI and carbon consumption unit when the amount of hydrogen gas injected is 100 Nm ³ /t (amount injected per ton of molten iron), and graph L11 is a linear connection of points P11. Point P12 shows the correlation between CRI and carbon consumption unit when the amount of hydrogen gas injected is 200 Nm ³ /t, and graph L12 is a linear connection of points P12. Point P13 shows the correlation between CRI and carbon consumption unit when the amount of hydrogen gas injected is 300 Nm ³ /t, and graph L13 is a linear connection of points P13. Point P14 shows the correlation between CRI and carbon consumption unit when the amount of hydrogen gas injected is 400 Nm ³ /t, and graph L14 is a linear connection of points P14. Therefore, graphs L10 to L14 correspond to correlation information. In the example of Fig. 1, the graphs L10 to L14 connecting the points P10 to P14 are used as the correlation information, but as shown in Fig. 2, approximate curves L20 to L24 of the points P10 to P14 may be calculated by, for example, the least squares method, and these may be used as the correlation information. In Fig. 2, the formulas and coefficient of determination ^R2 of the approximate curves L20 to L24 are shown.

According to Fig. 1, it can be seen that, in terms of the carbon consumption intensity, when the amount of hydrogen gas injected is small (up to 200 ^Nm3 /t), the higher the CRI, the better the result, and when the amount of hydrogen gas injected is increased (300 ^Nm3 /t or more), the lower the CRI, the better the result. The results in Fig. 1 show that the appropriate CRI value differs between normal operation or when a small amount of hydrogen gas is injected and when a large amount of hydrogen gas is injected. This finding is the most important point of this embodiment. It should be noted that the same result can be obtained even if the measurement is performed using the hydrogen concentration in the bosh gas instead of the amount of hydrogen gas injected.

The reason for this change is as described above. That is, during normal operation or when the amount of hydrogen gas injected is small, the reduction of iron-based raw materials is promoted by CO gas and hydrogen gas generated by the gasification reaction of coke (C+ _CO2⇒2CO , C+ _H2O⇒CO + _H2 ), and the proportion of direct reduction, which is a large endothermic reaction, decreases. Here, when the amount of hydrogen gas injected is small, the endothermic reaction by hydrogen reduction does not become the rate-limiting point of the heat balance in the furnace. Therefore, the carbon consumption rate decreases by increasing the reactivity of the coke.

On the other hand, when a large amount of hydrogen gas is injected, a large amount of hydrogen gas is present in the furnace, and hydrogen reduction is largely performed by the hydrogen gas. Therefore, the temperature in the furnace drops significantly, and the reduction rate of the iron-based raw materials by hydrogen gas and CO gas starts to decrease. In such a situation, if the reactivity of the coke is increased, it is considered that the adverse effect of the endothermic reaction (C + H ₂ O ⇒ CO + H ₂ ) caused by the gasification reaction of the coke becomes more significant than the effect of generating reducing gas by the gasification reaction of the coke. Therefore, when a large amount of hydrogen gas is injected, it is considered that the endothermic reaction caused by the gasification reaction of the coke is suppressed by lowering the reactivity of the coke, and thus the carbon consumption unit is reduced.

Here, the blowing temperature of the hydrogen gas is not particularly limited. In the example of FIG. 1, the blowing temperature of the hydrogen gas is room temperature (25°C). Here, the blowing temperature of the hydrogen-containing gas is the temperature of the hydrogen-containing gas when it is blown into the blast furnace from the tuyere. In actual operation (actual furnace), the set temperature of a heater (for example, installed in a gas tank) that heats the hydrogen-containing gas is the blowing temperature. In other words, the hydrogen-containing gas is heated by the heater (unheated at room temperature) and then blown into the blast furnace from the tuyere. The hydrogen-containing gas can be blown into the blast furnace from a tuyere for blowing hot air provided at the bottom of the furnace. In this case, the hydrogen-containing gas heated by the heater (or unheated) is mixed (merged) with the hot air generated from the hot air stove and then blown into the blast furnace from the tuyere. The temperature of the hydrogen-containing gas rises when it is mixed with the hot air, but the temperature at this time is not the blowing temperature in this embodiment.

(2-2. 2nd process)
In the second step, the appropriate value of the coke reactivity is determined based on the correlation information prepared in the first step and the amount of hydrogen-containing gas injected into the blast furnace or the hydrogen concentration in the bosh gas. That is, the amount of hydrogen-containing gas injected or the hydrogen concentration in the bosh gas in the actual operation is compared with the correlation information prepared in the first step to determine the appropriate value of the coke reactivity. For example, when the graphs L10 to L14 shown in FIG. 1 or the graphs L20 to L24 shown in FIG. 2 are prepared as correlation information, a graph corresponding to the amount of hydrogen-containing gas injected or the hydrogen concentration in the bosh gas in the actual operation is obtained. Then, the CRI at which the carbon consumption intensity is minimum (for example, corresponding to the inflection point of the graphs L20 to L24) is specified from the obtained graph, and the specified CRI may be set as the appropriate value of the coke reactivity. Alternatively, a point corresponding to the amount of hydrogen-containing gas injected or the hydrogen concentration in the bosh gas in the actual operation may be obtained from the points P10 to P14, and the reactivity of the coke at which the carbon consumption intensity is minimum may be specified from these points.

As another example of the method for determining the optimum value, for example, the following determination method can be mentioned. That is, first, the optimum value of the coke reactivity is determined for each correlation information. For example, the CRI that minimizes the carbon consumption unit is acquired as the optimum value from the graphs L10 to L14 or the graphs L20 to L24. Next, optimum value information showing the correlation between the total hydrogen input amount to the blast furnace or the hydrogen concentration in the bosh gas and the optimum value of the coke reactivity is created. An example of the optimum value information is shown in FIG. 3 and FIG. 4. The horizontal axis of FIG. 3 indicates the total hydrogen input amount to the blast furnace (Nm ³ /t), and the vertical axis indicates the CRI (%). The total hydrogen input amount is the total hydrogen (atom) amount input to the blast furnace per ton of molten iron converted into hydrogen gas. The total hydrogen amount is defined as the hydrogen amount contained in the hydrogen-containing gas + the hydrogen amount in the pulverized coal + the hydrogen amount derived from the blast moisture.

Point P30 indicates the optimum value of CRI for the total hydrogen input amount, and graph L30 is a graph in which points P30 are linearly connected. Therefore, graph L30 corresponds to the optimum value information. Of course, for example, an approximation curve of point P30 may be obtained by the least squares method, and this approximation curve may be used as the optimum value information. FIG. 4 is an example in which the horizontal axis of FIG. 3 indicates the hydrogen concentration (mol%) in the bosh gas. The horizontal axis of FIG. 4 indicates the hydrogen concentration (mol%) in the bosh gas, and the vertical axis indicates CRI (%). Point P40 indicates the optimum value of CRI for the hydrogen concentration in the bosh gas, and graph L40 is a graph in which points P40 are linearly connected. Therefore, graph L40 corresponds to the optimum value information. Of course, for example, an approximation curve of point P40 may be obtained by the least squares method, and this approximation curve may be used as the optimum value information.

Next, the optimum value of the coke reactivity is determined based on the optimum value information and the total amount of hydrogen input to the blast furnace or the hydrogen concentration in the bosh gas during actual operation. With this method, once the optimum value information is prepared, the first step can be omitted.

(3. Third step)
In the third step, the coke having the determined optimum value is charged into the blast furnace. It is preferable that the total amount of the coke to be charged has the optimum value. As described above, according to the present embodiment, the optimum value of the coke reactivity is determined according to the amount of hydrogen gas injected or the hydrogen concentration in the bosh gas, so that operation with further reduced _CO2 emissions is possible.

3. Modifications
5 shows the correlation between the reactivity of coke and the CO2 gas reduction information showing the effect of reducing CO2 gas when the hydrogen gas injection temperature is 1200°C or when a high-concentration hydrogen-containing gas ( _hydrogen gas 600 ^Nm3 /t + nitrogen gas 150 ^Nm3 /t, i.e., gas containing _hydrogen gas at 80 mol%) is injected into a blast furnace. The horizontal axis shows CRI (%), and the vertical axis shows carbon consumption intensity ( ^kg /t). Point P50 shows the correlation between CRI and carbon consumption intensity when the hydrogen gas injection amount is 200 ^Nm3 /t, point P51 shows the correlation between CRI and carbon consumption intensity when the hydrogen gas injection amount is 400 Nm3/t, and point P52 shows the correlation between CRI and carbon consumption intensity when the hydrogen gas injection amount is 600 ^Nm3 /t. The hydrogen gas blowing temperature at points P50 to P52 is 1200°C. Point P53 shows the correlation between CRI and carbon consumption unit when the high-concentration hydrogen-containing gas is blown. The blowing temperature at this time is 1200°C. As is clear from Figure 5, when the hydrogen gas blowing temperature is 1200°C or when high-concentration hydrogen-containing gas is blown into a blast furnace, the same correlation as in Figure 1 holds. Therefore, the above-mentioned blast furnace operation method is possible in these cases as well.

Next, an example of this embodiment will be described. In this example, a blast furnace operation simulation was performed to confirm that the above correlation holds.

<1. Models and calculation conditions used in the simulation>
For the blast furnace operation simulation, a so-called "blast furnace mathematical model" was used, as shown in Kouji TAKATANI, Takanobu INADA, Yutaka UJISAWA, "Three-dimensional Dynamic Simulator for Blast Furnace", ISIJ International, Vol. 39 (1999), No. 1, pp. 15-22, etc. This blast furnace mathematical model roughly divides the internal region of the blast furnace in the height direction, radial direction, and circumferential direction to define a plurality of meshes (small regions), and simulates the behavior of each mesh.

The calculation conditions are as shown in Table 1. Hydrogen gas was blown in from the tuyere. The production ratio is the amount of pig iron produced per 1 ^m3 of furnace volume per day, and the blast volume is the amount of hot blast blown in per minute. The oxygen enrichment rate is roughly the volume ratio of oxygen in the hot blast to the total volume of the hot blast, and is expressed as follows: Oxygen enrichment rate (%) = {(Air blast volume (flow rate) [ ^Nm3 /min] x 0.21 + Oxygen enrichment amount [ ^Nm3 /min]) / (Air blast volume [ ^Nm3 /min] + Oxygen enrichment amount [ ^Nm3 /min])} x 100-21. In actual operation, the oxygen enrichment rate is adjusted by changing the flow rate of enriched oxygen and the flow rate of air ( ^Nm3 /t) without changing the flow rate of oxygen ( ^Nm3 /t), which is the total flow rate of enriched oxygen and oxygen in the hot blast. This is to keep the pig iron production rate (the amount of pig iron produced per ^cubic meter of furnace volume per day) as constant as possible. The furnace top gas temperature is the temperature at the top of the blast furnace, the coke ratio is the amount of coke consumed per ton of molten iron (kg/t), and the pulverized coal injection rate is the amount of pulverized coal injected into the blast furnace per hour (ton/h).

In this example, the hydrogen gas injection rate was set to 0 to 600 ^Nm3 /t, the CRI was set to 20, 25, 30, 35, and 40 (%), and the specifications were designed so that the furnace top gas temperature was constant. In addition, the blast rate, oxygen enrichment rate, and pulverized coal injection rate were adjusted so that the pig iron tapping rate and molten iron temperature were constant in all cases. As a result, the correlation shown in Figure 1 was obtained. Therefore, it became clear that the above-mentioned blast furnace operation was possible.

The above describes in detail preferred embodiments of the present invention with reference to the attached drawings, but the present invention is not limited to such examples. It is clear that a person with ordinary knowledge in the technical field to which the present invention pertains can conceive of various modified or revised examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

Claims (4)

A first step of preparing correlation information showing a correlation between coke reactivity and _CO2 gas reduction information showing a _CO2 gas reduction effect for each amount of hydrogen-containing gas including hydrogen gas injected into a blast furnace or for each hydrogen concentration in a bosh gas;
A second step of determining an appropriate value of coke reactivity based on the correlation information and the amount of hydrogen-containing gas injected into the blast furnace or the hydrogen concentration in the bosh gas;
and a third step of charging coke having the determined optimum value into the blast furnace. The correlation information indicates a correlation between the reactivity of the coke and a carbon consumption unit,
2. The method for operating a blast furnace according to claim 1, characterized in that in the second step, the reactivity of the coke that minimizes the carbon consumption unit relative to the amount of hydrogen-containing gas injected into the blast furnace or the hydrogen concentration in the bosh gas is determined as the appropriate value of the reactivity of the coke. In the second step, optimum value information indicating a correlation between a total amount of hydrogen input to the blast furnace or a hydrogen concentration in the bosh gas and an optimum value of the reactivity of the coke is prepared,
3. The method for operating a blast furnace according to claim 1 or 2, characterized in that the optimum value of the coke reactivity is determined based on the optimum value information and a total amount of hydrogen input to the blast furnace or a hydrogen concentration in the bosh gas. In the first step, an approximation curve showing a correlation between the reactivity of the coke and the _CO2 gas reduction information is created as the correlation information;
The method for operating a blast furnace according to any one of claims 1 to 3, characterized in that, in the second step, the reactivity of the coke corresponding to an inflection point of the approximation curve is determined as an appropriate value of the reactivity of the coke.

Images